1. Field of the Invention
The present general inventive concept relates to an ink-jet image forming apparatus, and more particularly, to an ink-jet image forming apparatus and a method of controlling ink flow, which can decrease a risk of ink leakage through a print head and can easily remove foreign substances from the print head.
2. Description of the Related Art
An image forming apparatus is an apparatus that prints a black and white image or a color image on a printing medium, e.g., paper, according to an image signal, for example, a laser printer, an ink-jet printer, a copying machine, a multi-function printer, a fax machine, etc. An image forming apparatus is classified as an electrophotographic type in which a beam is scanned onto a photosensitive body to form an electrostatic latent image and a developer is adhered to the electrostatic latent image to transfer the same onto a printing medium, or an ink-jet type in which a liquid type ink is ejected onto a surface of a printing medium according to an image signal.
Of the above described types of image forming apparatuses, the ink-jet image forming apparatus is provided with a print head which ejects ink according to an image signal. By the print head ejecting an ink droplet according to an image signal, an image, such as letters or pictures, are printed on a printing medium. The ink-jet image forming apparatus is classified as a shuttle type in which a print head ejects ink while reciprocatingly moving in a direction (a width direction of a printing medium) perpendicular to a printing medium conveying direction, or an array type in which a print head having a length corresponding to a width of a printing medium is fixedly mounted above a printing medium conveying path to achieve line printing.
In such an ink-jet image forming apparatus, when ink is ejected from nozzles of the print head according to an image signal, ink stored in an ink tank is automatically supplied to the print head, and thus the print head can eject the ink successively. If an excessive amount of ink is supplied to the print head during a printing operation, or if the ink is supplied to the print head during a non-printing operation, a so-called wetting phenomenon may occur, in which the ink leaks out on a surface of the print head irrespectively of the printing operation. To prevent this problem, a regulator is mounted between the print head and the ink tank, which regulates ink flow so that the optimum amount of ink is supplied to the print head from the ink tank only when the ink is ejected from the print head.
FIG. 1 is a schematic view of a conventional ink-jet image forming apparatus, which illustrates only a print engine part to print an image on a printing medium by ejecting ink.
As illustrated in FIG. 1, a conventional ink-jet image forming apparatus includes a print head 11 having a plurality of nozzles (not shown) to eject ink, an ink tank 13 to store ink, a regulator 12 mounted between the print head 11 and the ink tank 13 to regulate ink flow, and an ink pump 14 to force ink to flow between the print head 11 and the ink tank 13.
In such a conventional ink-jet image forming apparatus, when the ink is ejected from the print head 11 according to an image signal, a passage in the regulator 12 is opened, and the ink in the ink tank 13 is supplied to the print head 11 through the regulator 12. In a non-printing operation state, the regulator 12 blocks the ink flow, and thus the ink in the print head 11 is prevented from flowing out of the print head 11. The ink pump 14 forcedly circulates the ink through the print head 11, the ink tank 13 and the regulator 12, thereby preventing the ink in the apparatus from becoming dry and hard.
However, in the above-described conventional ink-jet image forming apparatus, because the ink tank and the regulator are mounted above the print head, a positive pressure is always generated above the regulator. Therefore, when the regulator is left as it is for a long period of time, or when the regulator operates erroneously or is damaged, the ink in the ink tank may flow down to the print head, which results in leakage of the ink from the print head.
Also, the conventional ink-jet image forming apparatus has a problem such that it is difficult to remove air and dust existing in the print head 11 by discharging them to the outside. Because the ink pump 14 has only the function of circulating the ink, though the ink forcedly flows by the operation of the ink pump 14, it is difficult to remove foreign substances from the print head 11.